A length of optical fiber is wound about a hub of a spool in the form of an optical fiber coil. The optical fiber coil abuts against a flange of the spool. The optical fiber and the flange in one example are made from different materials. A temperature change causes the materials to expand. Because the different materials have different expansion coefficients, the optical fiber coil and the flange expand to different degrees. Since the optical fiber coil and the flange are in contact, the differential expansion must be absorbed by either or both of the optical fiber coil and the flange.
Where the flange is more rigid than the optical fiber coil, the flange serves to constrain expansion of a segment of the optical fiber coil located adjacent to the flange. That segment of the optical fiber coil constrained by the flange therefore expands differently than other segments of the optical fiber coil located further from the flange.
As one shortcoming, these differences in expansion between the segments of the optical fiber coil create sharp gradients in the strain of the optical fiber coil. As another shortcoming, the segment of the optical fiber coil located adjacent to the flange is deformed. As a further shortcoming, the deformation causes asymmetry in the optical fiber coil that results in movement, due to environmental causes such as temperature changes or stress due to vibration, in the optical midpoint as perceived by light passing through the optical fiber coil. This movement is represented by relatively large peak-to-peak thermal Shupe bias variations. Disadvantageously, such strain gradients negatively affect signal propagation by the optical fiber coil.
One design employs a buffer layer located only on the hub. The design lacks any additional buffer layer on any other part of the spool. As one shortcoming, the buffer layer located only on the hub has relatively little, if any, effect toward decreasing the strain gradients between the segment of the optical fiber coil located at the flange and the other segments of the optical fiber coil located further from the flange.
Thus, a need exists for enhanced promotion of a decrease of strain gradients in an optical fiber winding. A need also exists for promotion of a decrease of strain gradients between segments of an optical fiber winding located at different distances from a face coupled with a body, such as a flange of a spool. A further need exists for enhanced promotion of a decrease of deformation of an optical fiber winding.